1. Field of the Invention
The present invention relates to a liquid crystal polyester resin composition useful for forming to films or molded articles by injection molding or extrusion molding.
2. Description of the Prior Arts
Unlike crystalline polyesters such as polyethylene terephthalate and polybutylene terephthalate, a liquid crystal polyester consisting of rigid molecules does not become entangled even under the melting condition, but forms a polydomain in a liquid crystal state and has low shear properties to realize a remarkably high orientation of molecular chains towards the flow. So, the liquid crystal polyester is called thermotropic liquid crystal polymers. This specific behavior causes excellent melt flow properties and gives thin-wall molded articles of 0.2 through 0.5 mm in thickness having high strength and high rigidity easily. Molded articles of a liquid crystal polyester, on the other hand, have various disadvantages, including extremely large anisotropy. The insufficient vibration-damping properties and the high molding temperature undesirably restrict its applications to various fields. There have been a problem of manufacturing cost of a liquid crystal polyester.
In the market, there has been a strong demand for an improved liquid crystal polyester resin composition, which is manufactured at low cost and exhibits improved vibration-damping properties and anisotropy in the form of molded articles while maintaining the excellent heat resistance and mechanical properties of a liquid crystal polyester.
A resin composition disclosed in JP-A-56-115357 includes a melt processable polymer and an anisotropic melt processable polymer. The processabilities of a melt processable polymer have been enhanced by mixing an anisotropic melt processable polymer with the melt processable polymer. An example of such resin compositions is a mixture of polyphenylene ether and polystyrene blended with a liquid crystal polyester.
Another resin composition disclosed in JP-A-2-97555 is prepared by mixing a variety of polyarylene oxides with a liquid crystal polyester to improve the solder heat resistance.
Any conventional resin composition prepared by mixing a liquid crystal polyester of a high molding temperature with a non-crystalline polymer of a lower molding temperature, such as polyphenylene ether, results in poor appearance of molded articles due to pyrolysis of the resin mixture during the high-temperature molding while having the improved melt processability. Other drawbacks include insufficient heat resistance, mechanical properties, and impact resistance of the resulting composition.
Proposed resin compositions including a liquid crystal polyester and an aromatic polycarbonate, as disclosed in JP-A-57-40551 JP-A-2-102257, do not have sufficient heat resistance or mechanical properties.
JP-A-58-201850, JP-A-1-121357, JP-A-1-193351, the EP 67272/A2, and JP-A-7-304936 disclose a composition comprising a liquid crystal polymer applied with a copolymer of an .alpha.-olefin and, for example, glycidyl methacrylate. However, the composition needs further improvement in terms of mechanical properties such as impact resistance and tensile strength.
Furthermore, the U.S. Pat. No. 5,216,073 discloses a blended product comprising an epoxidated rubber applied with a liquid crystal polymer. However, the product is insufficient in heat resistance and mechanical properties.
On the other hand, liquid crystal polyesters have characteristics such as molecular orientation in the molten state owing to a strong molecular interaction. Therefore, application of the liquid crystal polyesters in the industrial field as a film material having functions such as a gas barrier property in addition to known properties such as excellent strength, elastic modulus and heat resistance has been desired.
However, unlike aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate, since rigidity of molecules in liquid crystal polyesters prevents entanglement even in a molten state and allows significant orientation of molecular chain to the aligned direction, they show behaviors such as drastic decline of the melt viscosity by slight shear increase and drastic decline of the melt viscosity by temperature rising, resulting in an extremely low melt tension in a molten state. Therefore, in the field of film molding or blow molding there is a problem of practicability due to difficulty in maintaining a certain shape in a molten state, and difficulty in balancing properties in longitude and latitude due to the molecular orientation, which may result in rupture in the alignment direction of the molecules. Accordingly, films comprising a liquid crystal polyester utilizing advantageous properties of liquid crystal polyesters has not been applied to a practical use sufficiently.
Concerning such liquid crystal polyesters, JP-A-52-1095787 and JP-A-58-317187 disclose a laminated product having uniaxially aligned liquid crystal polyester films attached so as to cancel a high anisotropy. However, such product is not efficient in terms of productivity and has a problem of peeling of the films.
The U.S. Pat. No. 4,975,312 and WO 9015706 disclose a technique to cancel the anisotropy of a liquid crystal polyester by a method of rotating ring dies, and JP-A-62-25513, JP-A-63-95930 and JP-A-63-24251 disclose a special technique in a T die method. However, these are methods of alleviating the anisotropy with a special molding method, and have drawbacks in practicability such as high cost and limitation in formation of a thin film.
JP-A-62-187033, JP-A-64-69323, JP-A-2-178016, JP-A-2-253919, JP-A-2-253920, and JP-A-253950 propose a multilayer (laminate) sheet comprising a liquid crystal polyester and a thermoplastic resin and a multilayer (lamination) film. However, these sheets have problems such as peeling caused by a large orientation of a liquid crystal polyester or by the existence of an adhesive layer between the layers, declining in properties inherent to a liquid crystal polyester such as gas barrier property and heat resistance, and difficulty in the thin film production.
On the other hand, an inflation film formation has been attempted for obtaining a liquid crystal polyester film having an alleviated anisotropy of a liquid crystal polymer and an excellent strength.
The inflation film formation method refers to a method in which a resin melt-kneaded in an extruder is extruded from a die having a circular slit to form a tubular molten product, which in turn is expanded by supplying certain amount of air therein while cooling periphery of the tube to produce a tubular film.
As examples thereof, JP-A-63-173620, JP-A-3-288623, JP-A-4-4126, JP-A-4-50233, and JP-A-4-49026 disclose a method of inflation film formation of a liquid crystal polyester. However, these film formation methods cannot be used widely since the methods require a special film formation device and a very severe condition owing to a characteristics of liquid crystal polyesters. Besides, films obtained in the methods have drawbacks such as insufficiency in stretching property, flexibility and gas barrier property, difficulty in thin film formation and high expenses.
Many researches and developments have been conducted on wrapping materials for pouching and standing pouching.
For example, JP-A-62-103139 discloses a wrapping material for retort pouching comprising a resin film having silicon dry-plated on the surface thereof.
JP-A-1-308826 discloses a wrapping material for retorted product mainly comprising an ethylene-vinyl alcohol copolymer.
JP-A-2-180129 discloses a retort pouch selected from the group consisting of an ethylene-vinyl alcohol copolymer film and a vinylidene chloride copolymer film.
Regarding aluminum deposition films or films having an inorganic material such as silicon deposited or coated thereon, many problems are pointed out such as inapplicability to a micro wave oven, insufficient heat resistance of a base resin film, and residual ash component after incineration.
Further, in the case of using a polyvinylidene chloride film, insufficiency in heat resistance in the retort processing, and a waste gas issue at the time of incineration after use are pointed out. In the case of using an ethylene-vinyl alcohol copolymer film, an ethylene-vinyl acetate copolymer film, or a polyester film, the films are insufficient in heat resistance, water vapor barrier property and water resistance.
On the other hand, although aluminum foil is broadly used as a wrapping material for pouching, they have many problems such as inapplicability to a micro wave oven or disposal by incineration, and sensitivity to a metal detector.
JP-A-2-261456, JP-A-5-278747, JP-A-7-237281, and JP-A-7-241967 disclose a standing pouch or a wrapping material comprising a multilayer laminated film.
However, as to multilayer laminated films, various problems, such as difficulty in production and generation of peeling-off between the layers, have not been solved so far.
Therefore, wrapping materials for pouching, with good gas barrier property and molding-processing property, and excellent heat resistance, and applicable to a micro wave oven, are strongly demanded in the market.
Although containers having a gas barrier property are broadly used in the industrial fields, conventional gas barrier type containers do not satisfy the needs of the market. That is, requirements toward a gas barrier type container include not only an excellent gas barrier property but also applicability to a micro wave oven, heat resistance for allowing the use as a wrapping material for a retorted food to endure heat processing, molding-processing property for facilitating film formation a the base of a container, recycling after use, and easy disposal. Conventional gas barrier type containers do not sufficiently satisfy these requirements.
For example, polypropylene is insufficient in terms of a gas barrier property, and an ethylene-vinyl acetate copolymer has a drastic decline of a gas barrier property in the moisture absorption and is insufficient in heat resistance. Poly(vinylidene chloride) has a low heat resistance, and further, has a problem in terms of environmental concern after disposal due to comprised chlorine.
Polyethylene terephthalate (hereinafter abbreviated as PET) is insufficient in terms of heat resistance and water vapor barrier property.
A gas barrier material comprising an ethylene-vinyl acetate copolymer or PET having an inorganic material such as silica and alumina deposited thereon, and a gas barrier material comprising a thermoplastic resin attached with an aluminum foil are insufficient in heat resistance, have a problem of peeling-off of a film, besides, in the case of a material comprising a metal, there is a problem of inapplicability to a micro wave oven.
Hollow molded containers comprising a resin having a light weight and a gas barrier property are used in the application for food, beverage, industrial chemicals and cosmetics. For example, hollow molded containers comprising an ethylene vinyl alcohol copolymer, vinylidene chloride or polyethylene terephthalate are known. However, hollow molded containers obtained by blow molding these resins are not sufficient in heat resistance and gas barrier property. Further, in the case of filling contents to a hollow molded container at a high temperature, or washing the container with a liquid of high temperature, the containers of these resins may not be sufficient in heat resistance.
Although liquid crystal polyesters have been known for having a good heat resistance and an excellent gas barrier property, it is quite difficult to have a good hollow molded container of a liquid crystal polyester by blow molding due to a large anisotropy and a low melt viscosity of liquid crystal polyesters.
Concerning molded bottles comprising a liquid crystal polyester or a liquid crystal polyester resin composition, JP-A-61-192762 discloses a hollow molded container obtained by melt-molding a resin composition comprising a liquid crystal polyester and a polyester having a specific structure.
JP-A-2-260646 and JP-A-3-269054 disclose a container having an excellent gas barrier property obtained by molding a blended product of polyethylene terephthalate and a liquid crystal.
JP-A-1-289826 discloses a molded article of a laminated product comprising a polyethylene terephthalate layer and a liquid crystal polyester layer. Further, JP-A-4-166320 discloses a production method of a container comprising a liquid crystal polyester having a specific structure.
However, in either case, due to poor molding processability of the resin, there are problems such as difficulty in producing a molded container having a good appearance, low production efficiency, and an insufficient gas barrier property of a container. And thus requirements from the market have not been sufficiently satisfied.
On the other hand, in the field of automobile industry, examination has been made for a long time on a plastic gasoline tank for a light weight, molding processability, strength and freer designing so as to meet the requests from the market.
For example, polyethylene is excellent in molding processability and strength, but insufficient in the gasoline barrier property, which is the barrier property with respect to gasoline.
JP-A-1-14049 discloses a fuel tank comprising a multilayer hollow molded article formed with a barrier layer comprising a material selected from the group consisting of polyamide, polyester and an ethylene-vinyl acetate copolymer, and a modified polyolefin layer.
JP-A-4-47938 discloses a fuel tank comprising a multilayer hollow molded article formed with a polyamide layer, a high density polyethylene layer, and a modified high density polyethylene layer.
However, these fuel tanks comprising a barrier layer of a polyamide layer are insufficient in the gasoline barrier property, and further insufficient in the barrier property with respect to an mixture fuel comprising alcohol such as methanol.
JP-A-6-191296 discloses a fuel tank for automobile of a hollow molded article comprising a multilayer structure with a barrier layer of a copolymer polyamide layer of aromatic polyamide and nylon 6, further comprising a modified high density polyethylene layer and a high density polyethylene layer.
Further, JP-A-6-218891 discloses a fuel tank for automobile of a multilayer molded article having a barrier layer of a blended product of polyethylene and polyamide.
JP-A-7-52333 discloses a fuel tank of a multilayer structure having a resin composition layer comprising an ethylene-vinyl alcohol copolymer applied with a thermoplastic resin. And JP-A-7-40998 discloses flame retardant foam plastic.
However, these fuel tanks have shortcomings such as insufficiency in gasoline barrier property or gasohol barrier property, which is the barrier property with respect to a mixture of gasoline and methanol, and the need of having a very thick resin layer so as to maintain a high barrier property.
Furthermore, various problems such as peeling between layers due to the multilayer structure of the tank exist, which have not been solved yet.
Since molded articles such as sheet and film of a foam resin are lightweight and comparatively strong, they are broadly used in the fields of wrapping material, construction material, industrial equipment, business equipment and cushion material. However, in particular, in the fields of electric or electronic equipment and automobile parts, a foam resin having heat resistance and mechanical properties superior to conventional products are desired in the market.
Liquid crystal polymers are resins basically capable of satisfying such required properties, and thus foam products thereof have been examined conventionally. For example, the U.S. Pat. No. 4,429,061 discloses a foam product of aromatic polyester, having a specific naphthalene skeleton structure. The Japanese Patent Publication Hei No. 2-42099 discloses a polymer foam product comprising a specific liquid crystal polymer. JP-A-3-179042 discloses a production method of a foam product of a liquid crystal polymer. Furthermore, the Japanese Patent Publication Hei No. 5-25901 discloses a foam product containing a liquid crystal polyester and an inert filler. JP-A-4-318039 discloses a liquid crystal polymer foam product defining a diameter of a cell of the foam product. The Japanese Patent Publication No. 7-74285 discloses a foam resin molded article comprising a liquid crystal polymer with a specific structure.
However, conventional liquid crystal polymer foam products still have problems such as a large anisotropy of the foam product, insufficiency in mechanical properties, poor appearance, and a high cost.